Ground trainer for aircraft personnel



F. M. PEARSALL.

Aug. 22, 1950 A 77`ORNE V Filed 001;. 12, 1945 COWL FLAPJ` F. M. PEARSALI. 2,519,698 GROUND TRAINER EoR AIRCRAFT PERSONNEL 5 Sheets-Sheet 2 /N TOR a 2R' By F M. PEARSALL A @am l ATTORNEY F. M. PEARsALL. 2,519,698

GROUND TRAINER FOR AIRCRAFT PERSONNEL Aug. 22, l195o Filed Got. l2, 1945 5 Sheets-Sheet 3 HYDRAULIC PRESSURE MOTOR UNIT `//V VE N TOR E M PEA/RMLL A TTOR/VE Y Aug.- 22, 1950 v F. M. PEARSALL GROUND TRAINER FOR AIRCRAFT PERSONNEL 5 Sheets-Sheet 4 Filed Oct. l2,` 1945 Aug. 22, 1950 F. M. PEARSALL GROUND TRAINER FOR AIRCRAFT PERSONNEL Filed Oct. l2, 1945 5 Sheets-Sheet 5 Qwwmw St /Nl/E/V l F M PEARSA/.L @a M A 7'7'ORNEV Patented ug. 22, 1795() UNITED STATES PATENT OFFICE GROUND TRAINER Fon AIRCRAFT rERsoNNEL Frank Mi Pearsall, Merrick, Y.; assig'nor to Bell Telephone Laboratories,

Incorporated, N W

York, N. Y., a corporation fof New York Application oototer' 12, 194%, "serial No. 622,069

34v claims; (C1. 35e- 12) Frnis invention relates to an operationaiflignt trainer and, more particularly, to circuits and apparatus `for simulating the operation 'ci the hydraulic system of an airplane and the niesponse oiy `the hydraulic pressure indicators to the simile lated cperation oflan engine driven compressor, pilotis emergency hand pump, and of nyolrauncally operated mechanisms such as the' Wing iiaps, engine couri flaps, landing gear and gun chargers.

The airplane `which the trainer is designed to simulate is provided with a hydraulic syst-ern `for furnishing hydraulic pressure tor the operation oi various mechanisms ci the airplane; The -hye draulic systemv is normally supplied with pressure by an engine driven hydraulic pump or coinpressr. For applying pressure from the system to operate apparatus hydraulic selector control valvesV operable by the pilotl are provided which permit the lowering' and retractioncf the landing gear, the operation of the wing flaps, the 'opa eration of the engine cowl flaps, the operation of the intercool'er and il cooler shutters, the operation of the wing locking pins and the operation oi the gun chargers. l

VThe engine driven bump Causes a hydraulic pressure to be built up in 'the system to 1500 p'un'ds' per square inch at which time an une leader valve functions to prevent further pres-V sure build-up. When the pressure falls below 1250 pounds per square inch the unloader valve returns to normal and the engine driven pump can again build up pressure.

If the regular engine driven pump system fails, the hydraulically Operated rnechahisns of the airplane may still be operated by means of an 'emergency' hand pump and a Vhand 'pump selector valve which provides connections overindi'vidual `hydraulic lines` tc permit the operation of the landing gear only, 'of the Wing nap only, or o'f the gun chargers, engine cowl naps' and Wing loci: pins, depending upon the position cf the Selectr valve and the Cldith of the individul hydraulic lilies.

VI'f the hydraulic system is completely disabled so that no hydraulic pressure may be received from the engine driven pump or from the emere gency hand pump, the landing gear may be Wa ered.v by rneans of an emergency compressed air system which consists of a compressed air bottie, air pressure gauge, T-handle control and a p separate pipe line from the bottle to the landing gear operating cylinders. n? V l it is the object of the present-invention to.

simulate the functioning of the hydraulic sys= 2 tern of an airplane in a ground trainer for pilot training.

In a trainer it is not desirable to duplicate the intricate and expensive mechanisms of an actual airplane which are hydraulically operated or to provide the hydraulic system which would be required to furnish the hydraulic power necessary to operate such mechanisms. Therefore simpler and less expensive electrical equipment isv provided which simulates the production of the requisitev hydraulicpressure, which simulates the application of hydraulic pressure tothe various pieces' 'oi hydraulically operated mechanism and which simulates the responses of such mecha nijsms. 4

in order that in so far as the pilot under training is concerned, all of the controls and apparatus which he 'sees in the cockpit of the fuselage oi the trainer shall have the same ap*- p'earance and shall have the same response 'to operation as the similar equipment of the airplane which' the trainer simulates, the actual controls and equipment or an airplane have been mdie'd to produce electrical rather than me'- cllariical or hydraulic effects upon their operation and the 'pressure gauges cr indicators which We d normally respond to hydraulic operation to indicate to the pilot the pressure in the hydraulic system or the pressure in the compressed air ereigeny bottle are operated by electrical telea metric'systerns. simulated in the traner, electric motor units are previdd which 'simulatev the prcduction of hydraulic pressure; the cperati'on of the landing gear, the operation of the engine cowl flaps, and the operatio'nbf the Wing Ya'ps. lrThe hydraulic p'rcss'uredrairi incident to the operation of the g'uii eliaiis is als simulated but no simula'- ticn di pressure drains incident to the 'opere atten or the interneeierand oil easier shutters or tc the operation or the wing locking pins are picyided since these operations are not required inthe nail-ici*a i For a better understanding of the invention',

reference may ne hasv to the renewing detailed description ivheii'read in connection with the accinpany'ing 'drawings in Which: l

Fig. i shcfit's inl the portion thereof to the left or the doti-dash line cockpit apparatus including the hydraulic pressure anddninp pressure indicaters entitlev pilots instrument paneii the einer@ g'iy hydraulic' h'tld alii h'ald Sei! lector valve, the emergency landing gear control and the air bottle and valve, and tc' the right Since the engine operation is" the wing iiaps manual control, the electrohydraulic wing fiaps control and the valve control motor operable by said latter control, and in the portion to the right of the dot-dash line the motor units which simulate the operation of the engine cowl flaps and the landing gear;

Fig. 5 shows in the upper left portion thereof, the motor unit which controls the operation of the wing naps indicators on the pilots and in the upper right portion thereof instructors instrument panels and the motor unit which simulates the operation oi the wing flaps, and in the `lower portion oi the ilgure other control relays mounted in the apparatus cabinets and the schematic representation of the RPM and indicated air speed moto-r units of the trainer; and

Fig. 6 is a diagram showing how the several iigures of the drawings should be assembled t completely disclose the invention.

The hand pump selector valve used in an actual airplane has been modied, as schematically disclosed in Fig. 1, by the removal of the valve and by the addition of four switch assemblies |00 to |03, inclusive, operable by cams mounted on a shaft |04 connected to the valve handle |05. The switch assemblies are selectively operated in diierent positions of the valve handle. Each of the switch assemblies comprises two l'iXed springs serving as iront and back contacts and a movable spring tensioned for engagement with the front Contact and carrying an operating stud of insulating material which rests on the surface of the associated cam to hold the movable spring out of contact with the front contact spring except when the cam is rotated to such a position that the end of the stud enters a notch in the periphery of the cam.

The hydraulic hand pump, schematically disclosed in Fig. l, is modied by the addition of a cam member |06 mounted on the pump handle |01 which, through a spring |08 secured to the casing of the pump, operates the spring assembly |09.

The emergency landing gear control, shown schematically in Fig. 1, comprises a T-handle ||0 movable on the pivot bolt |63 against the tension of the spring I I and in its operated position engageable with the lever ||2 also pivoted on bolt |63 to release the movable spring of the spring assembly H3 into its circuit closing position. In an actual airplane the handle I|0 operates a valve which permits compressed air from the air bottle ||4 to be forced into the hydraulic cylinder of the landing gear to lower the landing gear. The air bottle I I4 is a wooden mock-up of the air bottle of an actual airplane and the control valve which connects the bottle with the dump pressure indicator is simulated by the Valve screw II5 which when screwed in to a position representative of the closure of the bottle valve holds the spring assembly |I6 in its open position.

The cowl iiaps control used in an actual airplane has been modhed as schematically shown in Fig. 4 by the removal of the valve, the stem of which would be rotated by the T-handle 400 and by the substitution of two cams 40| and 402 operable by the handle to control the two switch assemblies 403 and 404. When the handle is moved to the right or open position the cam 402 permits the spring assembly 404 to operate to its alternate or circuit closing position and when the handle is moved to the left or closed position cam 40| permits the spring assembly 403 to operate to its alternate or circuit closing po sition.

The landing gear lcontrol used in an actual airplane has also been modied as Shown in Fig. 4 by the removal of the valve the stem of which would be rotated by the handle 405 and by the substitution of two cams 406 and 401 operable by the handle to control the two switch assemblies 408 and 40S. When the handle is moved to its lower or down position the cam 401 permits the release of the spring assembly 409 to its circuit closing position, as indicated, and when it is moved to its up position, indicated by dotted lines, the cam 405 permits the release of the spring assembly 408 to its circuit closing position. In an actual airplane when the airplane is on the ground the weight of the airplane on its landing wheels causes the operation of a locking device associated with the control handle 405 which prevents the movement of the handle from its landing gear down position to the landing gear up position so that the landing gear may not be retracted while the airplane is on the ground. This is simulated in the control used in the trainer by the provision oi a locking pin 4|0 which is forced into a hole in the hub of the handle 405 by the spring 4II when the handle is in the down position to prevent the movement of the handle to its up position. For retracting the pin to release the handle the solenoid 4|2 is provided which is energizable only when the simulated iiight has left the ground as represented by the operation of the flight (F) relay 500 of the indicated air speed motor unit 50| of Fig. 5.

The manual wing flaps control on an actual airplane has been schematically modified as shown in Fig. 4 by the removal of the valve the stem of which is rotated by the handle 4I3 and by the substitution of the cams 4|4 and 4|5 rotatable by the handle @I3 to operate the switch assemblies 4|6 and al1. When the handle is rotated to the iiaps down position cam 4|5 is rotated to a position in which it permits switch assembly 4|1 to release into its circuit closing position and when the handle is rotated to the flaps up position cam 4I4 is rotated to a position in which it permits switch 4|6 to release into its circuit closing position.

In the airplane the valve controlled by the manual wing flaps control may also be operated by an electric motor which may be controlled to run in one direction to operate the valve to its flaps down position and to run in the opposite direction to operate the valve to the flaps up position under the 4control of a switch located on the left side of the cockpit. This equipment is simulated in the trainer by a motor unit controlled by the switch 4I8. The motor unit comprises a reversible series-connected split eld direct current motor 4|9 geared through reduction gearing 420 to a shaft 42| which controls cam operated limit switches 422 and 423 to limit the operation of the motor in either direction in response to the operation of the control switch by energizing itsstator vwinding and short-circuiting oneY of its shaded Vpole windings and to rotate in the opposite direction by energizingits stator 4winding and short-circuiting its other shaded. pole winding. The motor 504 through the reduction gear box 505 drives the shaft 506 which in turn drives the cams of limit switches L| and L2 and the slider of potentiometer 501. The potentiometer 501 controls the wing aps portion of the position indicators 204 and 450 on the instructors and pilots instrument panels to show the position of the wing flaps.

The cowl flaps motor unit shown in the uppe right portion of Fig. 4 is of similar construction to the wing flaps indicator motor unit and also employs a reversible alternating current motor 424 of the shaded pole type.

The landing gear motor unit shown in the lower right portion of Fig. 4 is in general similar to the wing iiaps indicator motor unit and is driven by a reversible alternating current motor 428 of the shadedpole type. The shaft 430, in addition to driving the cams for operating the limit switches Ll and L2 also drives the cam which operates the switch assembly L3 vwhen the shaft 430 is in a position representative of the condition in which the landing gear is about 40 per cent retracted, and through gearing drives the sliders of a plurality of potentiometers of which three 43|, 432

and 433 have been disclosed herein. These potentiometers together with the LGD and LGU relays 434 and 435` control'the landing gear portions of the position indicators 204 and 460 on the instructors and pilots instrument panels to show the positions of the right, left and tail wheels of the landing gear.

The apparatus employed in carrying out the invention having now been described, the operation of the apparatus in training a pilot Will now be discussed.

It will be assumed that the hydraulic system is functioning properly and that the hand pump selector valve handle |05 has been operated into the SYS position in which position in an actual airplane the hydraulically operated apparatus would be operable by the hydraulic pressure supplied to the hydraulic system by the engine driven pump. In this position a circuit is established from ground over the contacts of switch assembly v|00, now closed, over conductor |22 and through the winding of the SYS relay 205 to battery. Relay 205 upon operating simulates the closure oi the hand pump selector valve to the SYS position and such operation is indicated by the closure of the circuitV from ground over the lower No. l contacts of relayr205 and through the System lamp at the instructors desk to battery.

When the pilot has operated the proper switches and controls of the trainer to simulate the starting of the engine, the RPM motor unit 502 will be operated in the manner fully described in the application of C. E. Germanton, Serial No. 622,070 led concurrently herewith, to rotate its shaft 508 Ito a position representative of the simulated engine speed. When the shaft 508 leaves its normal position, the cam 500 driven by the shaft operates the spring assembly 510 to its alternate position in which the circuit of the ON relay 5|| is established indicative of the fact that the engine is then running and driving the hydraulic pressure pump driven thereby. The operation of relay 5| now establishes the circuit of a potential divider which may be traced from the 40 p| busbar, through resistance 5I2, over the contacts of relay. .511, overconductor 513, over.. the Yupper 8` back contacts of the unloader valve (UNV) relay |23, over conductor |24, over the inner upper back contact of the DHL relay 206, over the back contact of the DHS relay 201 and to ground through resistance 208.

Potential of phase gol derived from this potential divider is applied over conductor 209 and through resistor AI to control conductor 302 of the hydraulic motor control circuit of Fig. 3. This signal potential is applied through the control rheostat 346 to the control grid of the left unit of voltage amplifying tube 30|, is amplified by the two units of such tube connected in cascade, and the amplified potential is impressed upon the primary winding of input transformer 303. Transformer 303 steps up this potential and applies it to the plates of the full wave rectiiier tube 304 and to the control grid of the gaslled motor reversing tube 306. The signal potential as rectified by the tube 304 is impressed upon the control grid of the gas-filled motor impulsing tube 305. As previously stated the tubes 305 and 303 are biased just below their critical breakdown or firing potential by positive biasing potential applied to their control grids under the control of the rectifier tube 304 and the bias adjusting rheostats 309 and 3|0. As a result of the application of the rectified signal potential applied to the control grid of tube 305, tube 305 will become conducting during each positive half wave of the plate potential applied from the source 3|2 through choke coil 3|3 to its plate and an impulse of positive current will iiow from the source 3l2, over the plate-cathode path through the tube 305 to the mid-tap of the middle secondary winding of transformer 301, thence through the rotor circuit of motor 300, over the back contact of the LS relay 32| and to ground. At the same time the potential applied to the control grid of tube 306 being of phase p2 which is opposite in phase to the plate potential applied to the plate of tube 306, tube 306 does not fire and the RV relay 3|5 consequently does not operate to cause the operation of the RVI relay 320.

With relay 320 unoperated the stator winding of motor 300 is energized over a circuit extending from the -l-lSO-volt battery 3|8, through ballast lamp 3|9, over the inner upper back contact of relay 320, through the stator Winding of motor 300, over the upper back contact of relay 320, over the normally closed contacts of limit switch L2 and to ground. The motor thus has its stator WindingV energized in such a direction that in response to the current impulses transmitted through .its rotor winding under the control of tube 305, as previously described, the motor rotates in such a direction that, through the reduction gear box 322, shaft 323 is rotated at a slow speed in a direction indicative of the production of an increasing hydraulic pressure in the hydraulic system. This increasing pressure is indicated on the hydraulic pressure indicators H9 and Ziii on the pilots and instructors instrument panels through the operation of the synchrotransmitter 335 driven by the shaft 323 through the gears 330 and 33|, and the synchroreceivers ||8 and 200.

When the motor shaft 323 reaches a position corresponding to a pressure of 1250 pounds per square inch the cam 320 operates the switch assembly 334 to its alternate position in which it will remain should the pressure continue to increase to 1750 pounds per square inch. With the switch assembly 334 thus operated a circuit is established from ground over the contacts of such switch assembly, over conductor 34'| and through the winding of the HP relay |25 to battery. Relay |25 now operates andover its upper No. 2 contacts establishes an obvious circuit for the auxiliary HPI relay |20. The operation of these relays simulates thev increase of pressure in the hydraulic system to a high enough value to permit the operation of any of the ,hydraulically operated mechanism of anairplane.

As the motor driven shaft 323 continues to rotate and reaches a position corresponding to a pressure of 1500 pounds per square inch, the cam 329 operates the switch assembly 335 to its alternate position in which it will remain should the pressure continue to increase to 1750 pounds per square inch. With the switch assembly 335 thus o perated a circuit is established from ground over the contacts of the switch assembly, over conductor 348 and through the winding of the UNV relay |23' to battery. Relay |23, which simulates the operation. of the unloader valve of the hydraulic system of an airplane when the hydraulic pressure Ahas been built `up' to 1500 pounds per square inch, now operates and at its back; contacts opens the potentialdivi'der from which signal potential of phase was derived and applied to control conductor 302 of the hydraulic pressure motor control circuit of Fig. 3.

`With the signal potential removed tube 305 ceases to fire and motor 300 comes to rest. Shaft 323 is now stopped in a position representative of a pressure of lpounds per square inch and the lindicators H9 and 20| will indicate this presrapid-1y during the warming up period unless the air temperature is very low, the `pilot operates the engine cowl flaps control handle 400 to the open position to y hydraulically control the opening of the: cowl naps.. In the trainer this is simulated by the operation of the cowl flaps control handle 400 to the open position there- .by rotating the cam 402 into a position permitting the spring assembly 404 to move to its alternate positon. A circuit is thereby established from ground over the: contacts of switch assembly 404, oyerficonductor 4138, over the upper back contact ofthe CO relay 431, vover the normally closed .contacts of `the limit `switch assembly L2 and Vthrough the winding of the O relay 438 to battery. Relay 438'upon operating shunts the Vrigh-t shaded'pole winding 430 of the motor 424 and-with the stator windingv of the motor energized from the supply source of` L15-volt alternating currentpthe motor 424, through the reduction gear box 425, turns the shaft 426 at a slow speed in a counter-clockwise direction representative of the opening of the cowl flaps. The

shaft continues rotating so long as the control switch wis held in the open position or until the cam 440 of theLZ limit switch opens the circuit of relay e30 to` thereby stop the: motor.

Relay V438 when operated also establishes a .circuit from ground over its lower contacts and conductors 44| through theV winding of the CF relay |21'- tobatteryf Relay |21 upon operating establishes a potential divider circuit from the 402 bus-bar, through resistance 2|0, over the lower No. 3 contacts of the SYS relay 205,y over conductor 2| i, over the lower contacts of relay |21 and through resistance |28 to ground. From this potential divider potential of phase p2 is derived and applied over conductor |29 and through resistor A4 to control conductor 302 of the hydraulicV pressure motor control circuit. This potential simulates the hydraulic pressure drain which would result in an airplane by apply- `ing hydraulic pressure to the cylinder which operates the engine cowl ilaps. In response to this potential the motor 300 of the motor control circuit rotates the shaft 323 in a direction representative of a reduction in hydraulic pressure which will be indicated by the pressure indicators H9 and 20|. lf, as assumed', the pressure in the hydraulic system is 1500 pounds per square inch, that pressure will now drop to just below 1250 pounds per square inch due tothe simulation of the opening of the cowl naps.

The shaft 323 vhas now rotated cam 328 into a position in which the spring assembly 334 is released thereby releasing the HP relay |25 followed by therelease'of the HPl relay |26. Relay |26 upon releasing opens the locking circuit of the UNV rel-ay 23 and since the initial operating circuit ior relay |23 is opened at the contacts 'of spring assembly 335, relay |23 now releases and re-establishestheV previously traced circuit over which the engine pump signal of phase pi was applied through resistor AI to conductor 302 of the hydraulic pressure motor control circuit. Motor 300 is now operated to rotate shaft 323 in a direction representative of an increase in pressure, cam 328 again operates the spring assembly 334 to cause the-reoperation of relays 25 and t2@ when a simulated pressure above 1250 pounds per square inch is attained, and cam 329 again operates the spring assembly 335 to cause the reoperation of the UNV relay 23 which removes the phase qll engine pump signal from control conductor 302 oi the hydraulic pressure motor control circuit to stop the motor 300 when a pressure above 1500 pounds per square inch is again attained.

With the phase q engine pump signal removed, the cowl fla-ps drain signal oi phase p2 again reduces the pressure to just below 1250 pounds per square inch whereupon the engine pumpV signal of phase ol is again cut in and the pressure increases. This cycle continues until the flaps are fully operated and the release of the O relay 438 removes the phase p2 drain signal. During the' ilaps operation there will be less than two cycles' of hydraulic pressure operationas just described and the pointers ofthe indicators H0 and 20| will oscillate between 1250 and 1500 pounds per square inch.

The instructor is informed concerning the operation of the cowl naps control 400 tothe open position by the lighting of the Cowl Flaps Open lamp at the instructors desk over a circuit extending vfrom ground over contacts of switch assembly 404 and over conductor 535 through the Cowl Flaps Open lamp to battery.

Wing flaps operated to the up position Before simulating a take-oil the pilot operates the wing flaps control switch 4 8 to its up `posi-- tion thereby establishing a circuit from ground over the UP contacts of such switch, over conductor 442 and to battery through the winding of I the.V UP relay 5|4. Assuming that the pilot has 1l previously closed the circuit breaker 443 thereby establishing a circuit rfrom ground through resistance 444, over contacts of the circuit breaker and over conductor 445 to battery through the `:winding of circuit breaker (BKR) relay I5 to operate relay 5I5, the operation of relay 5I4 is effective to establish a circuit from ground through the armature circuit and right eldwinding of motor M9, over the contacts of limit switch 422, over conductor 5I6, over the upper contacts of relay 5M, over the lower contacts of relay 5I 5, over conductor 5I1 and to battery over the contacts of the cut-off switch at the instrctors desk. The motor 4 I 0 through the gear box 420 now operates to turn the shaft 42! at a slow speed in a direction representative of the naps up position. When the shaft is rotated to a position representing a full up position of the flaps the cam V446 operates the spring assembly 422 to open the circuit of the motor 4IS which then stops. During the time relay 5I@ is operated a circuit is established from ground over its lower contacts and over conductor 5i8 to battery through the Wing Flaps Electric Up lamp, at the instructors desk to inform the instructor that the wing iiaps are being moved to their up position under electrohydraulic control.

As a further result of the operation of motor 4 I 9, the shaft 441 of the Wing Flaps Manual Control is turned to a position in which the cam 4M permits the closure of the contacts of spring assembly 4I5 thereby establishing a circuit from ground thereoven over conductor 448 and through the winding of the EUP relay 5I9 to battery. Relay 5I9 upon operating establishes a circuit from ground over its lower contacts and conductor 520 to battery through the Wing Flaps Manual Up lamp at the instructors desk to inform the instructor that the apsrare being moved Vto their up position. Relay 519 also establishes a circuit `for the FU relay 52I which may be traced from battery through the winding of such relay, over the upper contacts of relay 5I9, over conductor 53I, over the lower No. 4 contacts of the SYS relay 205, over conductor 2 I 2, over the upper back contact of the F relay |30, since the assumed flight is notnyet airborne, over the lower No. 2 back contact of the low pressure (LP) relay I3I, which is not operated since the hydraulic system has been assumed to have a pressure greater than '300 pounds per square inch, over conductor I32, and to ground at the lower No. 3 back contact of the SCO relay 2I3.

Relay 52I upon operating establishes a potential divider circuit from the 40m2 bus-bar, over the upper front contact of relay 52I and through resistances 522 and 523 to ground, from which potential divider a potential is derived and applied through the resistor 524 to the signal input conductor 525 of the wing iiaps motor control circuit 503. Under the control of the control circuit 503 the motor thereof rotates the shaft 520 in a direction representative of the movement of the aps to their up position and since the potentiometer 521 driven by the shaft 520 has been rendered ineffective by the opening of the energizing circuit therefor at the upper back contact of relay 52I, the motor rotates the shaft 526 into the position representative of a fully up position of the wing flaps or until the potentiometer slider is at the No. 1 terminal of its winding, at which time the circuit of the motor is opened by the limit switch (not shown) in a manner described in connection with the motor control circuit of Fig. 3.

Relay 52| also establishes a circuit from ground,

vIl!! and 20|.

the LI limit switch of the wing flaps indicator vmotor unit, which would be in its released position,'and through the winding of the FUI relay 528 to battery. Relay 528 thereupon operates to establish over its upper contacts a shunt of the left shaded pole winding of motor 504 and, since the stator winding of the motor is energized by current from the -vo1t alternating current supply, the motor will operate to turn the shaft 500 in a direction representative of the movement of the wing flaps to their up position until the limit switch LI operates to the position shown in Ythe drawingto release relay 528 and to thereby stop the motor. A locking circuit is nowestablished for relay 52I which may be traced from battery through its winding over the back contact of the EDN relay 538 released, over the alternate .contacts of the LI limit switch of the wing flaps indicator motor unit and to ground at the lower contacts of relay 52I. Thus, if the flaps are in their full up position, the loss of hydraulic pressurewill not cause relay 52I to release and cause the flaps motor unit 503 to assume some posi- `tionfaway from the full up position.

The rotation of the shaft 506 in a clockwise direction to the limit of. its movement, results in the movement of the slider of potentiometer 501 to the No. 1 terminal of its winding. The winding of potentiometer 501 is connected over conductors 529 and 530 to the end terminals of the windings of the telemetric receivers of the indi- -cators 400 and 204 in the cockpit and at the instructors desk. With the INST circuit breaker 2M on the pilots electrical distribution panel ,closedto establish the circuit of the INST circuit breaker relay 2 I 5 over a circuit from ground, through resistance 2I6, through the circuit breaker and winding of relay 2I5 to battery, operating battery is Ysupplied over the contacts of relay 2I 5 and conductor 2I1 to the junction point between the windings ofthe telemetric receivers of the indicators 400 and 204. The windings of the vreceivers and the winding of potentiometer 501 serve as a direct current telemetric system .so that as the slider of potentiometer 501, which is connected through resistance 534 to ground, moves the permanent magnet rotors of the telemetric receivers in the indicators move pointers thereof to positions corresponding to the posi- -tion of the slider of potentiometer 501, or the lsimulated position of the wing iiaps. Vindicators are only incidentally concerned with Since the the present invention a full disclosure thereof is not deemed essential herein.

In addition, relay 528 establishes a potential divider circuit which may be traced from the 405112 bus-bar through resistance 2I8, over the ylower No. 2 back contact of the SCO relay 2| 3,

conductor 536 and through resistor A5 to control conductor 302 of the hydraulic pressure motor control circuit. This signal simulates the 4hydraulic pressure drain which would result in an Vairplane by applying hydraulic pressure to the wing flaps operating cylinders. In response to this signal the motor 300 of the motor control circuit rotates the shaft 323 in a direction representative of Va reduction in hydraulic pressure which will be indicated by the pressure indicators Assuming that the pressure in the hydraulic system is 1500 pounds per square inch,

l the operating circuit of the LPI relayv |`4| but this relay remains locked up over its inner upper contacts, over conductor |44 and to groundrat the upper contacts of the LGO relay 456 associated with the landing gear motor unit.

The LGO relay 456 upon operating also establishes a circuit from ground over its inner'lo-wer contacts, over the normally closed contacts of the limit switch L3, over the contacts of limitswitch LI, in its released position and through the right shadedV pole winding of motor 428 to ground, whereupon the motor 428 through the gear box 429 turns the shaft 43|] in a direction representative of the retracting of the landing gear. This movement will continue until a position is reached representative of the condition when the landing wheels would be about 40 per cent retracted or corresponding to theposition to which the landing gear wheels would retract rapidly, due to the action of the slip stream, at which time the circuit of the motor is opened by the operation of the L3 limit switch and the motor stops. During this time the simulated hydraulic pressure has dropped to a value less than 300 pounds per square inch and until the pressure has again been'built up to about 1250 pounds per square inch the HP' relay |25 will not be operated and no alternative circuit for operating the motor 428 will be effective. When, however, the pressure has again been increased to 1250 pounds per square inch and relay |25 again operates and with the LP| relay |'4| locked up, a circuit is established from ground over the upper No. 3 contacts of the SYS relay 205, over the lower No. 1 contacts of the LGR relay 220 over conductor 235, over the lower contacts of the LPI relay |4|, over the lower No. 2 contacts of the HP relay |25, over conductor |33, over the contacts of the L| limit switch and through the right shaded pole winding of motor 428 to ground. The motor then again operates to rotate shaft 430' at a slow speed in a direction representative of the movement of the landing wheels to their up position. The rotation of the sliders of potentiometers 43|, 432 and 433 by the shaft 430 controls the operation of the direct current telemetric receivers of the indicators 204 and 460 to move the right, left and tail wheel indicators to positions indicative of the retracted but unlocked positions of the wheels of the landing gear.

When the shaft439 has reached a position representative of the movement of the wheels'to their retracted position, the limit switchLl is operated to its alternate position in which the right shaded pol@ winding of motor 428 is opened and the motor stops. At this time ground on conductor |33 is applied over the alternate contacts of the L! switch assembly, through the winding oi the LGU relay 435 to battery whereupon relay 435 operates, locks over its lower front contact and conductor 45| to ground at the lower No. 2 contacts of the LGR relay 22|) and over its upper contacts short-circuits the resistances 452, 453 and 454 which are normally connected between the No. l terminals of the windings of the potentiometers 43|', 432 and 433 and the telemetric receivers of the indicators 204 and 450. The short-circuiting of these resistances causes the telemetric rec-eivers of the indicators 234 and 46B to receive an increase of operating current causing the red tabs on the indicating members of such indicators to disappear indicative of Ythe fact that the wheels have been locked in their fully retracted positions. Since the indicators are only incidentally concerned with the present inby the rotation of shaft 323 reaches a value of 1500 pounds per square inch when the UNV relay |23 will operate to remove the phase p| engine pump signal from control conductor 302 of the motor control circuit.

Closing engine cowl japs After the take-01T, the pilot will operate the cowl flaps handle 400 to the close position and hold it in such position for about six seconds. With the handle in such position cam 45| permits the operation of spring assembly 403 to its alternate position thereby establishing a circuit from ground thereover, over conductor 451 to battery through the C'owl Flaps Closed lamp at the instructors desk to inform the instructor that the engine cowl flaps are being closed and establishing a circuit from conductor 451 over the lower contacts of relay 431 of the cowl flaps motor unit, over the contacts of limit switch L| now closed and through the winding of the C relay 458 to battery. Relay 458 thereupon operates to short-circuit the left shaded pole winding of motor 424 to thereby cause the motor to drive the shaft 426 in a direction representative of the closing of the cowl iaps so long as the control handle 485 is held in the close position. Should the shaft rotate to a position representative of the vfully closed position of the ilaps the LI limit switch will open the circuit of relay 458 and stop the motor 424.

As a result of the operation of relay 458 the previously traced circuit for the CF relay |21 is established and relay |21 upon operating causes the application of cowl flaps drain signal of phase p2 through resistor A4 to control conductor 302 of the hydraulic pressure motor control circuit. The motor 300 then functions to cause the shaft 323 to rotate in a direction representative of a decrease in hydraulic pressure simulating the decrease in pressure incident to the closing of the cowl flaps. The hydraulic pressure circuit functions in the same manner as previously described in connection with the control of the opening of the cowl flaps.

Operation o the gun chargers If during the course of the simulated flight the pilot should operate the gun chargers as fully described in the Patent No. 2,459,867 granted January 25, 1949 to R. B. Buchanan, the RLS relay |36 will be operated each time a gun charger knob is depressed to charge or to safety the guns and will establish a potential divider circuit from the 40q 2 bus-bar over conductor 225, through resistance |31, over contacts of relay |33 and to ground through resistance |38 from which a gun charger drain signal of phase p2 is derived and applied over conductor |39 and through resistor A3 to control conductor 302 of the hydraulic pressure motor control circuit. This drain signal will cause the motor 30|] to turn the shaft 323 in a direction representative of a slight drop in hydraulic pressure. This drop in pressure will not ordinarily be sufficient to cause the establishment of the engine pump signal circuit if the 17' simulated' pressure is at 1500 pounds per square inch. Y J

v(rpe'r'ztz'on of wing flaps to the down position A When a simulated landing is to be made the pilot operates the' wing flaps electrohydraulic control switch fils to the"down position thereby establishinga circuit from ground over the contactsl of the switch, over conductor 459 and through the winding of the DN relay 533 to battery. Relay 533 operates and establishes a circuit from'ground through the armature circuit and` lef-,t eld windingof motor 4|9, over the contacts ofy springl assembly 423, overconductor over the `upper contacts of relay 533, over the lower contacts of relay 5|5, over conductor 5|? andy to battery over the contacts of the Cut-01T switch at. the instructors desk. The motor 4|9 through the gearbox 420 operates to turn the shaft 42| in a direction representative of a flaps down condition. When the shaft has reached a position representing a full down position of the flaps requiredfor landing, the cam 462 opens thespring assembly 423to open the' circuit of the motor 4 9 which then stops. During the time that relay 533` is operated a circuit is established from ground over its lower contacts and over conductor, 531 to battery through the Wing Flaps EleetricgDovvns` lamp at the instructors desk to inform the instructor that the wing aps are being movedto their down position under electrohydraulic control;

`As 4'a further result of the operation` of the motor 4|9 the shaft `441 of thev Wing Flaps Manual Control is moved to aposition in which the cam Mpermits the closure of the contacts of the spring assembly 4H thereby establishing a circuit from ground thereover, over conductor 453 and throughthe winding of the EDN relay 538 .to battery. Relay 538 upon operating .establishes-acircuit from ground over its lower contactsfand conductor `539 to battery through the Wing Flaps Manual Down lamp at the instructors desk to inform the instructor that the aps are beingvmoved to their down position. Relay 538 also establishesV a circuit for the FD relay 540, which may be traced from battery through the windingof such relay, over the contacts of thespring` assembly-54 i` of the indicated air speed motor unit operated as indicated if Athe air speed is `less than 17|)v knots, over the upper contacts of relay 538, over conductor, 53|, over thelower No. ,4; contacts ofthe SYS relay 205,over ,conductor 2|2, over the upper front contact of the F relay, |30, sincevethe flight isgassumed to be airborne, over the upper back contact of the MP relay |40, over conductorl I32yand to ground at the lower. No. 3 back contact'of the SCO relayV Relay 540- upon operating establishes a potential divider circuit from4 the 40e! bus-bar,

over the upper contacts .of relay 545 and through resistances 542 and 543 to groundfrom which potential divider a potential is derived and applied throughztheresistor -544 to the signal input conductor 525 ofthe wing flaps motor control circuit 503. Under the control of thecontrol circuit the motor vthereof rotates the shaft 525' in a direction representative of themovement ofthe jflapsto their down position. t Themovement of theshaftalso drives the slider of potentiometer 526 toward the No. Sterrninal of thelpoleltiometer winding and since this windingisenergized overa circuit yfromthe 40 p| busbar through resistance 546 over the upperback contact. of relay 52| and through the potentiometer winding to ground, a potential of phase pl is applied from the slider of the potentiometer through resistor 545 to control conductor 525. The potentials applied through resistors 554` and 545 are ofthe vsame phase and are balanced" against the potential ofv phase p2 derived at the slider of the indicated air speed vari-ac 552 which is applied to conductor 525 through resistor The winding of' variac 552' is energized from the irez 'eus-bar when vthe As relay 55s is operated i' to indicate air speed. These signals are so proportionedthat if the air speed is less than knots the motor of the wing flaps motor unit will drive the shaft 525 'to the full down position, but

at air speeds between 100 and 170 knots the motor will cause `shaft 525 to assume a position away from full down depending upon the speed and reaching a position corresponding to a 20-degree deflection at knots.

Relay 540 also establishes a circuit from ground over its lower contacts, over the contacts ofthe L2 limit switch of the wing flaps indicator motor unit and through the winding'of the lDirelay 54T to battery. Relay 54T thereupon operates to establish` over its upper contacts a shunt of the right shaded pole Winding of vmotor 50:3 andthe motor, then drives the shaft 506'in a direction representative of the movement of the wing ilaps to their 'down position and through the potentiometer 50i controls theV wing flaps indicator pointers of the indicators ZilllandV itil-'to show the movement of the Wing flaps in theirdown position.

In addition, relay 541 establishes a potential divider circuit which may be traced from theY drain which would result in the airplane by applying hydraulic pressure to the Wing aps operating cylinders. In response to this signal, the motor 300 of the motor control circuit rotates the shaft 323 in a direction representative of a reduction in hydraulic pressure which will be indicated by the pressure indicators H9 and 25|. The indicator needles will oscillate between 1250 and 1500v pounds per square inch during the time the wing' ilaps indicator motor unit is moving the shaft 506 to its down position, showing adrain on the hydraulic system due to wing flaps operation and the rebuilding of pressure by the engine driven pump. These oscillations are produced in the manner previously described in connection with the simulated movement of the wing flaps to their up positions.` e

` When thewing iiaps have been moved to their full vdown positions the Wing Flaps Electric Down lamp at the instructors desk and the Wing Flaps Manual Down lamp remain lighted so long as the wing flaps are maintained in their down position. When the shaft '505 of. the wing iiaps indicator motor unit reaches a position representative of thefull down position of the wing flaps, the L2 limit switch contacts are opened Vto release relay 541, whereupon the motor 504 stops and the wing aps drain signal is removed from theV control conductor of thehydraulic pressure motorv Control circuit.

i9 Landing gear to the down position" With the wing naps in their down position theyserve as airbreaks to help reduce the air speed of the airplane for landing. With the air speed reduced, the pilot operates the landing gear control handle 405 to its down position thereby opening the circuit over the switch assembly 408 to release the LGR relay 220 whereupon the Landing Gear Retract lamp at the instructors desk becomes extinguished and the LGU relay 435 of the landing gear motor unit becomes released. With the handle 405 in its down position, the cam 401 releases the switch assembly 409 to its circuit closing position thereby establishing a circuit from ground thereover, over conductor 464 and through the winding of the LGL relay 226 to battery. Relay 226, upon operating, establishes an obvious circuit for the Landing Gear Extend lamp at the instructors desk to inform the instructor that the pilot has taken steps to lower the landing gear.

Relay 226 also establishes a circuit from ground over the upper No. 3 contacts of the SYS relay 205, over the upper No. 1 contacts of the LQL relay 225, over conductor 22|, over the upper No. 3 contacts of the HP relay |25, it being assumed that the pressure in the hydraulic system is over 1250 pounds per square inch, over the upper back contact of theY HS relay |45, over conductor |46, over the contacts of the L2 limit switch of the landing gear motor unit in its released position and thence through the left shaded pole winding of the motor 428 to ground. With the left shaded pole winding of the motor thus shunted and the stator winding energized from the supply source of ||5 volts, the motor 428 is rotated and through the gear box 429 turns the shaft 430 at a slow speed in a direction representative of the movement of the landing wheels to their down positions. The rotation of the sliders of potentiometers 43|, 432, and 433 by the shaft 430 controls the operation of the direct current telemetric receivers of the indicators 204 and 460 to move the right, left and tail wheel indicators to positions indicative of the extended but not locked positions of the wheels of the landing gear.

When the shaft 430 has reached the position representative of the movement of the wheels to their extended positions, the limit switch L2 is operated to its alternate position in which the left shaded pole winding of motor 428 is opened and the motor stops. At this time ground is connected from conductor |46, over the alternate contacts of thevLZ switch assembly, through the winding of the LGD relay 434 to battery, whereupon relay 434 operates, locking over its lower front contact and conductor 41| to ground, over the upper No. 2 contacts of the LGL relay 225. Over its upper contacts relay 434 short circuits the resistances 468, 459 and 410 connected between the No.Y 3 terminals of the windings of the potentiometers 43|, 432 and 433 and the windings of the telemetric receivers of the indicators 204 and 460 and thereby increases the operating current through the windings of the telemetric receivers to cause them to operate their associated indicators to the full limits of their movements.

As a further result of the operation of relay 22S, a landing gear drain signal of phase p2 is applied overconductor 224 and through resistor A6 to control conductor 302 of the hydraulic pressure motor control circuit. This potential is derived from the potential divider circuit which is established from the 401102 bus-bar, over con'-c ductor 532, through resistance 455, over the lower back contact ofthe LGD relay 434, until the landing gear is fully extended, over conductor 45S, over the upper No. 1 contactsof the HIP relay |25, over the lower contacts of the UNV relay |23, over conductor |34, over the No. l contacts of the SYS relay 205, over the lower No. 2 contacts of relay 226 and to ground through resistance 223. motor unit is being operated to simulate the extension of the landing gear and until such simulated extension has been completed as represented by the operation of relayY 434, the motor 300 of the hydraulic pressure motor control circuit rotates the shaft 323 in a direction representative of a reduction in hydraulic pressure in simulation of the application of hydraulic pressure to the landing gear operating cylinders.

When the hydraulic pressure decreases to 1250 pounds per square inch, relays |25', |26 and |23 release as previously described. Relay |25, upon releasing, opens the potential divider circuit from which the landing gear drain signal of phase (p2 was derived and relay |23 upon releasing reapplies the engine pump signal of phase p| to the hydraulic pressure motor control circuit with the result that the motor 300 thereof now operates to rotate the shaft 323 in a direction representative of an increase in hydraulic pressure. WhenV the pressure again reaches 1250 pounds per square inch the spring assembly 334 is reoperated ton cause the reoperation of relays |25 and |26. With these relays reoperated, and relay |23 still unoperated, the resistance |35 is included in the potential divider from which the phase p2 drain signal was derived and applied to the A6 resistor to control conductor 302. As a consequence, a greatly decreased drain signal is applied in opposition to the engine pump signal and the jump signal being greater will cause the simulated hydraulic pressure to increase slowly while the extension of the landing gear continues. The combination of signals is used to simulate the approximation of one hydraulic cycle during the operation of the landing gear.

During this operation, the simulated pressure may build up to 1500 pounds per square inch thereby causing the operation of the UNV relay |23 as previously described to entirely remove the pump signal whereupon the motor 300 will respond only to the drain signal and the simulated pressure will start decreasing as before. When the landing gear is fully extended and the LGD relay 434 has operated, the drain signal is removed at its lower back contact. The simulated hydraulic pressure may now remain somewhere between 1250 and 1500 pounds per square inch or it may build-up to 1500 pounds per square inch again depending upon whether relay |23 is operated or not, as determined by the position of shaft cam-329.

Hand pump operation Hand pump operation of the hydraulically operated mechanisms of an airplane may be used when the airplane is grounded and the engine is not driving the engine driven pump or during flight should the engine fail or the hydraulic system fail to function. In the trainer, the instructor may simulate the failure of the main hydraulic system by opening the SYS Open key thereby establishing an obvious circuit for the DHS relay 201. Relay 20T,` upon operating. opens Thus while the landing gearv atf.itsi:back.-cotact the .previously tracedl circuit citer".wl-iichthe4 engine pump signal of phase pl wasiapplied-throughf resistor AI- to control conductor 302 of the hydraulic pressure motor controlcircuit` andat its front contact yestablishes au potential divider* circuit extending from the Mlqrbusebar, through resistance 23|, over the upperrNo.` 44 contacts of the SYS relay205, over theifront contact of relayl 201 and to ground through resistance 208. From this potential divider a1 heavy drain signal of phase p2 isiderivede` and.; applied over conductor 209 and through resistor Al to control conductor 302 whereby the motor300 is controlled to rotate the shaft1-323= back to normal in which positionthe pressure indicators ||9 and 20| `will show zero hydraulic pressure.

' Nows in order tooperate hydraulically controlledgmechanisms theA pilots must operate the hanrl` Dump :Selector valve tothe proper position andiuse the handtpump. If the. SYS Open key at theinstructors deskv is operated when the selector valve `is in any other position than the SYS 'position andztheSYS relay 205 is released, the operatipnfiof'`r the DHS relay 291 will remove the engine-pumpsignal but will not cause ythe hy.-

draulicpressurefmotor control circuit to operate in response. to a drain signal to reduce the simulated pressurexto Zero. Consequently,` the pilot mayyuse lthe controlsuntil their operation reduces thesimulated pressure to a degree where operationis no'y longer possible and at which point hand pump operation becomes necessary;

Sinceg the hand pump selector valve handle may` buildup pressure in the` hydraulic system by operatingfthe .pump handle |05 through several strokes; Each time that `the handle is raised, the carniIG'permits `the spring assembly le?) to move tojiitsivalternateposition thereby establishing a circuit `from ground over. the contacts of the springgassembly,` over conductor lill and through thewinding of the HDF relay 232 to battery and each timeathe handle is lowered, the cam |06 operatesthe spring assembly |59 to its other position. thereby establishing'a circuit from ground over: contacts oftheassembly, over conductor |48 anditoifbattery through the winding Aof the HDP! relay'233; Relays 232'. and 233 thus'operate in alternation andbeing slow to release establish a circuit over their iower contacts and through thefwinding of the I-IDPZ relay 234 so that relay 23.4 operatesand-releases inresponse to theoperationsofl, the-pumphandle Relay 234, upon operating,t establishes` an obvious circuitl for. the

Handilumpiamp at the instructorsdesk toin-V form theuinstructorthat the pilot has resorted to hand', pump, operation. f

Hundpumpoperation ofthe wing flaps It willfbe assumedthat the pilot has operated the hand: pump selector valve handle |05 tothe WF Only position, for example, to operate the wing., flaps, to. their down position. With the handle |05 in this position, a circuit is established front-ground' over the contacts of spring assembly;

|02, over conductor` |49 and through the winding oflthe: WF relay 235 to battery'. With relay 235 operated, an obvious circuit is established for the Wing Flaps lamp at'the instructors desk to inv form 'theinstructor that the pilot is operatingthe wingiiapfs-.by hand pump operation. A potential diyidereircuit isalso Aestablished under the con-r trol of the HDP2 relay 234fand relay 235 which man pragmatism the 4.0i* Weber. @meuse resistancezill, oven-,conductor 549, over.v the perzcontactsv` or relay 234, over` the lower backv Contact of relay 236, over. the lower contacts of theel/VF relay; 235, over conductor 236, over the.

lower front contact of the F relay itt, assuming thai-,fthe flight is airborne, over tlielower contacts oftheMP relay |130, which remains operated until the hand pump has created a simulated pressure of overV 800 pounds per square inch, and through resistance itilv to ground. A hand pump signaler `phase cpi is derived from this potential divider f andi; kapplied over conductor |5| and through resistor A2 to Vcontrol conductor 302 of the hydraulic pressure motor control circuit. In response to this signal the motor 300 turns the shaft 3235111 a direction representative of an increasing pressure until, when a pressure of over 800 pounds per square inch is attained, cam 321 permits the switch asszrnbly 333 to open and thereby open the circuit extending thereover and over conductor through the winding of the MP` relay lff-ato'battery. Relay l@ will then release and open the hand pump signal circuit just traced :thus stabilizingV the pressure at`800 pounds per square inch. -Y

The pilot may now operate the wing flaps con-` trol switch IHB, for example, to its down position therebycausing the operation of the DN relay 533 `which causes thelighting of the Wing Flaps Electric DownV lamp at the instructors desk and the operationvof the motor H9 of the valve control motor to move the Manual Control H3` into its down position to thereby cause the operation oi the EDN relay 538 all in the manner previously described. Relay 538 upon operating:

causes` .the lighting of the Wing Flaps Manual Down lamp at the' instructors desk and, with the M12' relay i) released representative o1" the adequate pressure oi 800 pounds per square inch to operate'the wing ilaps, a circuit is established' from ground over the middle lower contacts of the HDPZ relay'i over conductor |32, over the upper back contact of the MP relay U50, over the upperfrontcontact ofthe F relay 35, over conductor 2|2, overthe 'upper No. l. contacts ofthe WF relay 235,'over conductor 53|, over the inner upper contacts of relay, over contacts of the spring assembly 5M of the indicated air speed motor "unit 56E and through the winding or" the' FD relay 540 to battery. Relay Mil thereupon opi crates to control the wing flaps motor control circuit 503 and the wing iiaps indicator motor unit-inthe manner previously described.

Inresponse to the operation of the wing flaps indicator motor unit, the indicators 201| and 46!! are controlledto show the movement of the wing flaps to their down positions. YNo wing flaps drain signal is in this case applied to the control conductor 302 of the hydraulic pressure motor control' circuit when the FDI relay 51|? operates since the potential divider circuit which would be established upon the operation of relay 54'! is opened at the lower No. 2 back Contact of the SCO relay 223. Relay 2 I3 was energized upon the'rst operation of the HD? and HDPi'relays 232 and 233 over a circuit extending from battery through upper No'. 2 contacts of the WF relay 2,35 "and toj ground at the upper back contact `ofthe DHLV relayY 2%.

fl-d operate thawing fiaps while the apidocs.

on the ground a pressure of only 300 pounds per square inch is necessary and in the trainer when such pressure has been simulated by the operation of the hand pump and the motor 300 has rotated the shaft 323 to a position representative of 300 pounds per square inch, cam 326 permits the LP relay |31 to release and, when relay 538 is operated as previously described in response to the operation of the manual flaps control 413 to the down position, the circuit for operating the FD relay of the wing naps motor control circuit 503 is established from ground over the middle lower contacts of the lHDPZ relay 234, over conductor 132, over the lower No. 2 back contact of the LP relay 13 1, over the upper back contact of the F relay 130, released when the ight is grounded, over conductor 212, over the inner upper contacts of the WF relay 235, over conductor 53|, over the inner upper contacts of relay 538, over contacts of spring assembly 54| of the indicated airspeed motor unit and through the winding of the FD relay 5150 to battery. The apparatus then functions to simulate the operation of the Wing fiaps and to indicate the position which they have attained in a manner previously described.

Had the pilot operated the control switch 418 to the up position, the apparatus would have functioned in a similar manner to simulate the movement of the wing aps to their up position under the control of the UP relay 5113, the EUP relay 519, the FU relay 521, the FUI relay 528, the HDPZ relay 234, the WF relay 235 and the MP relay |40 or the LP relay 13| as previously described.

Hand pump operation of landing gear It will now be assumed that the pilot has operated the hand pump selector valve handle |05 to the LG Only position, for example, to retract the landing gear. With the handle |05 in this position, a circuit is established from ground over the contacts of spring assembly over conductor 152 and through the winding of the LG relay 23'1 to battery. With relay 231 operated an obvious circuit is established over its upper No. 4 contacts for the landing gear Hyd Sel LG lamp at the instructors desk to inform the instructor that the pilot is operating the landing gear under the control of the hand pump selector valve and hand pump. A potential divider circuit is also established under the control of relay 23'1 and the I-IDP2 relay 234 when operated, as previously described, through the operation of the pump handle |01, which circuit may be traced from the ce1 bus-bar, through resistance 58, over conductor 569, over the upper contacts of relay 234, over the lower back contact of relay 200, over the lower No. 1 contacts of the LG relay 23'1, over conductor 238, over the inner upper back contact of the HP1 relay 126 and through resistance |50 to ground. A hand Apump signal of phase qui is derived from this potential divider and applied over conductor and through resistor A2 to control conductor 302 of the hydraulic pressure motor control circuit.

In response to this signal, the motor 300 turns the shaft 323 in a direction representative of an increasing pressure until when a pressure over 1250 pounds per square inch is attained, cam 328 operates the spring assembly 331i to cause the operation of the HP relay |25 followed by the operation of the HP1 relay |26. Relay 126, upon operating, opens at its inner upper back contact the circuit just traced, over which the hand pump signal was applied to control -conductor 302 of the hydraulic pressure motorcontrol circuit and the motor 300 comes to rest, thus stabilizing the simulated pressure vat 1250 pounds per square inch.

Since this pressure is adequate Afor the operation of the-landing gear, the pilot may simulate the retraction of the landing gear by the operation of the control handle 405 to its up position if, as it will be assumed, the handle has been unlocked -by the solenoid |312 responsive vto a simulatedairborne ilight. Theoperationof the handle. 405 to its up position establishes the circuit of the LGR relay 220 as previously. described which causes the lighting of the Landing Gear Retract lamp at the instructors deskA to inform the instructor that the pilot is retracting the landing gear.

Upon the rst stroke of the hand pump and the consequent operation of the HDP and HDPl relays 232 and 233, the circuit of the SCO relay 213 is established and such relay, upon operating, locks over its upper No. l contacts, over theupper No. 3 contacts of the LG relay 231 and'to ground at the upper back contact of the DHL relay 206 and prevents the application of a landing gear drain signal to the hydraulic pressure motor control circuit as will be later described.

As a further result of the operation of the LG relay 231 and the LGR relay 220, a circuit is established from ground, over the middle lower contacts of the HDP2 relay 231i, over the upper No. 1 contacts of relay 231, over the lower No. l contacts of relay 220, over the inner upper contacts of relay 23d, over conductor |62, over the lower No. 2 contacts of the HP relay |25, now operated since it has been assumed that through hand p-ump operation pressure cf 1250 pounds per square inch has been attained, over conductor |33, over the contacts of the L1 limit switch in its released position and through the right shaded pole winding of the motor 428 of the landing gear motor unit to ground. The motor 428 now operates to turn shaft 430 in a direction representative of the retraction of the landing gear which retraction is indicated by the indicators 204 and 460 are previously described. rEhe circuits concerned with the retraction ofthe landing gear now function in the manner previously described in connection with the landing gear retraction under the hydraulic system control.

Since relay 466 is not operated under hand pump operation, the circuit .previously traced from the ftqn bus-bar, over conductor 532, through resistance 455, over the upper inner contacts of relay 463, over conductor 431', over the upper back contact of relay 1131 and through resistance |32 to ground, is not established and no drain signal is applied to the hydraulic pressure motor control circuit to simulate the reduction in hydraulic pressure incident to the retraction of the landing gear. Consequently, the simulated pressure does not fall belen/1250 pounds per square inch. Y

To lower the landing gear by hand pump operation the simulated hydraulic pressure `is increased to 1250 pounds per square inch by hand pump operation as previously described and the control handle M35 is operated to its down position thereby causing the operation of the LGL relay 226.

t With relay 223 operated a circuit is established from ground over the lower middle contacts of the HDPE relay 234, over the upper No. 1 contacts of the LG relay 231, over the upper No, 1 contacts ofthe VLGL relay 226, over conductor 22|;v over the-upper No. ,3 contacts of the HPV-relay I 25, oyerthe lupper'back contact of the HS relay |45, over conductor |46-, over the contacts of limit switchLZ andl through theleft shaded pole winding of motor 428 to ground. The motor functions in the manner previously ydescribed and when the shaft 432 reaches the limit of its movement, limit switch L-Zcperates to stop the motor andf-tocause the operation of relay 434.

Relay 226, uponoperating, attempts to esta lslr the potential divider extending from the 4il p2 bus-bar, over conductor 532, through resistance 455; over the lower back contact of relay 434, until the-landinggear is fully extended, over conductor 456, over the upper No. 1 contacts of the HP re lay |25, through resistance S35, over the lower back contact of the UNVrelay |23, over conductor |34, over the lower No. 2 contacts of relay 231, over the upper No. 3 back contact of the SCO relayY 213gV over `the -lower No. 2 contacts ofthe LGL relay 223 and through resistance 223 to ground, but this circuit is open atv the upper No. 3 hack contact'of the SCO relay 2|3 which operated as previously described in response to the first stroke ofthehand pump. Consequently no drain signal isfappliied through resistor A6 to the hydrauli'cpressure motor control circuit and the simulated' hydraulic pressure does not fall below 1250 pounds per square inch.

H and `pump operation of cocvlrflaps Itfwill-now be assumed that the pilot has operatedthev .hand pump selectorvalve handle to `theGrC--C1-WI.| position, fory example, toz close `flaps controllano to its closemposition thereby es,-

tablishing. the previously traced circuit for the motor 424' of' thecowl flaps motor unit to, simulate the operation ofthe cowl naps to their closed position, However, -until the simulatedl hydraulic pressure has been .built-up above 300pounds per Ysquare inchl bythe operation of the hand pump, the cowl-"naps control is ineffective tocontrol'the motory 424 fbecausetlfie LP relay I3! will be energized underthe control of cam '326.Y on shaft 32e-of: the hydraulicpressure motor control vcircuit and-'Twill hold the C@ relay 4310i the cowl Vila-psvmotorlunit operated izo-'prevent the operation` offtherC relay `llliil 'to close'the circuit of motorY 4241i The circuit of: the CO relay 43-1may be traced from battery through its windingover conductor4'12 and toground over the upper No. 2

front contact of the LP relay |3.-|

In ,response tothe operation of the hand pump handle 4|-|.1, thei'I-IDP and HDPI- relays 232 and `233 operate in alternation and the HDP2 relay 234 will; repeatedly operate and release -asfgpreviously described. Relay 234,.upon.its first-:operation, Awill establish the circuit of the SCO relay 2,.|3-,as reviously described'whereupon relay ,1213 .Willoperate and lock over its upper No. vl 4contacts, Aover the upper No. 2 fcontacts of thesGC relay 2.39,and to groundat the upperbaokcontact ofthe `DHL relay 203. Untila simulated vpressure greater than1300 pounds vper square inch `-is .1a-ttained,each.operation oiftheiHlDPZ rela-y 231iE es-- tablishesza potential divider circuit which may be tracedfrom the fill p| bus-bar, through resistance 548; over conductor 5451, over the upper contacts oi relay 234, over the lower back Contact of relay 206, over the lower No. 3 contacts of the GC relay 239over conductor 24B, over the'upper back contact of` the CF relay |21, over the lower contacts of'the MP relay '43, which will be operated with the sinfiulatedA pressure below 800 pounds per square inch, andfthrough resistance |50 to ground from which potential divider a hand pumpsignal is applied over conductor |51' and through resistor A2 to controlconductor 302. of thehydraulic pressure motor control circuit. In response to this hand pump signal, the motor 300 will turn the shaft 323 in a direction representative ofan increase in pressure.

Assoon as the shaft 323 has beenrotated toxa position representative ofa pressure greater than 300A pounds per square inch, cam 32E opens the circuit of the LP relay 63| which releases and in turn places the CO relay 431 under the control of the HDPE relay 2:34 to render the C relay 458 of the cowl flaps motor unit responsive tothe cowl flaps control 49) assumed to have been operated toits close position whereupon the motor 424 is operated in simulation of theclosin-g of the cowl flaps and acircuit is established-from ground over the lower contacts of relay 458 and over conductor 44| through the winding of the CF relay |21- to battery. Relay |211; upon operating, now opens the previousiytraced potential divider circuit to'remove the hand pump signalV from control conductor 302 of' the hydraulic pressure motor control circuit.

With the LP relay I3! now deenergized the next time thatthe HDP2 relay 234 releases during the operation of the hand pump a circuit is estabflished from ground over: the lower back contact of relay 234, over the lower-No. 4 contacts of the VSCO relay 2 I3, over thelower No. l contacts of the GC relay 239, over conductor 24 over the upper back contact ofthe LP relay |31, over conductor 412 and through the winding ofthe lCO relay 431 of the'cowl flaps motor unit so that relay 431 now operates and releases the CA relay 458V to stop the motor 434 and to release the CF relay |22. Relay |2f1 upon releasing again reestablishes the potential divider circuit from which the hand pump signalr was vderived and applied to the control'conductor 392 of the hydraulic pressure motor control circuit as soon as the HDP2 relay 234 again operates. On the next release -ofV relay 234, relay 43"! again operates to permit the response of the cowl flaps motor 424 and to reoperate relay |21 which again opensthe potential 'divider circuit to stop the application of the hand. pump signal; Thus the, motor 4,24 isoperated intermittently until the shaft 426 controlled thereby has moved to a position representative of the full closed positionof the -cowl ilaps. This simulates the stepby-step closure of the cowl ilaps under hand pump operation in an actual airplane.

Gun, charging under (hand pump yoperation,

For gun charging under hand pump operation, the hand pump selector valve handle |35 is moved to the GC-CF--WL positionthereby causing the operation of the GC relay 239 as previously described. The CF' relay |21 does not become operated atthis time since the cowl naps control 430 i-s not operated. Therefore, in response to the operation of the HDP, HDP! and HDPZ relays 232, 233and`234, the potential divider circuit previouslyy traced `overthe lower'contacts of the MP relay .Mais maintained until the motor 3530 of the hydraulic pressure motor control circuit has rotated the shaft 323 into a position representative or a pressure above 800 pounds per square inch and the MP relay |43 becomes released through the operation of cam 321. When relay |40 releases, it establishes a circuit whi-ch maybe traced from ground over its inner upper back Contact, over conductor |54, over the upper No. 3 contacts of the GC relay 239, over conductor |55 and to battery through the winding of the H-P relay |55 of the gun charger circuit. The operation of this relay as fully described in the application of R. B. Buchanan hereinbefore referred to is necessary 'for the initial charging or safetying of the guns. The gun charging drain potential of the phase 02 derived by the operation of the RLS relay is not cut off by the operation of the SCO relay 2|3 so that the hydraulic motor control circuit will be operated representative of a slight drop in pressure each time that a gun charger knob is depressed for charging or safetyin-g the guns.

As previously stated, it may be desirable to operate the hydraulically operated mechanisms of an airplane while it is on the ground and the engine is not running. For this purpose the hand pump selector valve is placed in the SYS position and the hand pump is operated. With the Valve handle |35 in the SYS position the SYS relay 235 is operated as previously described. The instructors controls must be normal and the wing flaps control switch 4 i 3 or hand control 4|3 must-be in the up position thereby causing the operation of the EUP relay 5|9 as previously described. Under these conditions when the hand pump is operated and the HDP, HDPI and HDPZ relays 232, 233 and 234 are op erated, a potential divider circuit is established which may be traced from the wel bus-bar, through resistance 54B, over conductor 549, over the upper contacts of the I-IDP2 relay 234, over the lower contacts of the DHL relay 255, through the 10,000-ohm resistance 242, over the lower No. 2 contacts of the SYS relay 255, over conductor |5'l and through resistance |52 to ground from which potential divider a hand pump signal ci phase el is derived and applied over conductor |5| and through resistor A2 to the hydraulic pressure motor control circuit. This signal will be lower than the hand pump signal previously considered to represent the slow build-up of pressure by the hand pump when. pressure is being supplied therefrom to the whole hydraulic system rather than over an individual line to hydraulically operated equipment when the hand pump selector valve is operated to one of its other selection positions.

Disabling the hydraulic system The instructor may completely disable the hydraulic system by operating the Line Open key thereby causing the operation of the DHL relay 206. Upon operating relay 2&6 opens at its lower back contact a point in the previously traced po 28 of a hydraulic leak. Relay 205 at its inner lower back Contact opens the operating circuit and at its upper back Contact opens the locking circuit of the SCO relay 2|3 so that'l such relay may not be operated and locked.

Emergency landing gear dump air pressure system As previously stated, this dump air pressure system in an airplane consists of a compressed air bottle and associatedvalves and connections to the landing gear hydraulic cylinders. It can only be used for lowering the landing gear and is normally never used unless the regular and auxiliary hydraulic pressure systems fail.

In the trainer the compressed air bottle valve is represented by the switch assembly ||6 which is in the open position so long as the compressed air bottle valve control is closed. Under this condition the dump air pressure (DAP) relay 343 is released and the zero pounds per square inch synchrotransmitter 331 is connected with the.

synchroreceivers |25 and 242 as previously described. The transmitter 331 is so adjusted that under this condition the receivers |28 and 202 will operate the associated dump air pressure indicators 52| Vand 263 at the pilots and instructors instrument panels to read zero pressure. To check the bottle pressure, the pilot opens the valve l5 associated with the mock-up I4 of the air bottle, thereby permitting the switch ||6 to close and establish a circuit from ground thereover, over the lower No. 3 back contact of the ELI relay 243 and over conductor 244 through the winding of the DAP relay 343 to battery. Relay 343 thereupon operates to'disconnect the synchroreceivers |25 and 232 from the synchrotransmitter 331 and to connect them with the synchrotransmitter 338 which transmitter is so adjusted as to cause-the receivers |2|J and 292 to set the dump air pressure indicators |2I and 203 to read 1800 pounds per square inch pressure.

To lower the landing gear -under air pressure control from the air bottle, the pilot operates the emergency landing gear control ||0 thereby closing the contacts of switch assembly ||3 to establish a circuit from ground thereover, over conductor |58 and through the winding of the EL relay 222 to battery. Relay 222 thereupon operates to establish over its lower contacts an obvious circuit for the ELl relay 243 which operates and locks over the lower contacts of the locking ground release (LK) relay 245. Relay 222 also establishes over its inner upper contacts an obvious circuit for the Emer-Lowering lamp at the instructors desk to inform the instructor that the pilot has resorted to the use of the emergency landing gear control. At its upper back contact relay 222 opens the circuit of the LGR relay 224 so that it will be possible for the pilot to make an emergency lowering of the landing gear, regardless of the position of the regular landing gear control.

Relay 243 at its lower No. 3 back contact opens the circuit of the DAP relay 343 and establishes a circuit from ground over the normal contacts of the dump pressure cut-off key 246 at the instructors desk, over its lower No. l contacts, over conductor 241, over the upper back contact of HSI relay 59, over the upper back contact of the HS relay |45, if the air speed is not greater than knots and relays |59 and |45 have not operated, thence over conductor |46 and over the contacts of limit switch L2 to ground through the left shaded pole winding of the motor 428. The motor 428 thereupon operates to turn shaft fair-speed isxgreatfer than f1.4() fknots. `:uponpperating opens the operating-circuit over iconductor-|46 for controlling the motor 428 "and @gastarse 'fdirection representative refr thelowering lorf-the"` andin'glge'arlwheels @to .their full' down position# flin'i which position the -LGD` relay `434 operates. "The indicatorsl204 and 4B!) are con trolled`fby'the ipotentiometers 43|,"5432.. and 433 andby 'the relay/#mitov indicate the full down cause the circuitV fior controlling the-:motor 428 Wil'lvbeppened by 4the operationfof the HS and HSI relays*|45z'andil59." 'The `circuit 01E-relay |45 may betracedrfrom battery throughxits winding over conductor "|50 and to groundsovercontacts of thespring assembly operated by camA 55|)n of the indicated `air 'speed'iniotor lunit 50| when the Relay |45 establishes an: obvious v'circuit for the HS! 'relay |59 .whichfalsoiyopensthecircuit over conductor llo` and locks over :conductor r| 6 to ground over the-lowerH-No. 2-contactso`f theELl'relay 243 if such Vrelay `hasioperated,'thus yif thedowering operation-of the `landingigear is being performed -byw-the lemergency` systeml and' relay'Z'l-"S is operlated, relay-v |59` vis locked zupr and even though the 1' air speed `shou'ldthereafter bexreduced below 140 knots-,and relayi|45 bereleased',"the .landing gear could notibe-.loweredall the wayxdown. However, lif'thefEloWeringf-,is :being d'onefby `the hydraulic orf auxiliary hydraulic system nitmayf be llowered al1 the Way down since relayed-Maand i551 were bothreleased after'the vair speed is reducedbelow `14o-knots.

, yDisable/tg The instructor may; prevent regular hydraulic system` operation by closing the SYS Open key as preyiously described `and mayr prevent auxilyiary"liy'draulic system operation by closing the fLine Open'jley as'previously described. To disable'the `emergency landing gear system, the in- Vstructoroperates the Dump Press Cut Off Key `l24|to the oi position thereby preventing the ELI vrelay 243 from establishingthe circuit for operating the motor 428 of the landing gear motor'unitl Ii' relay 243 has" been operated and ilcked, `it maybe released when the instructor Vupon the'completion of the ,training session re- 'storeskall operated relaysof the trainer to normal `by the `operation -ofthe LK relay 245 through vthe operation of the keyli.

nThe instructor may disable the electrohydraulic wing flaps vcontrol system by opening the Cut Off rkey or by vcausing the BKR relay 555 to release thereby removing battery by Which the valve control motor' lli Sis run under controlof theelectrohydraulic control switch 4 8. The wing flaps 'may then'be controlled by the maniualcontrol handle-aia l Automatic loperation of the wing flaps y If thawing flaps are down and the air speed 'exceedslOG knots, thevariac`552 of the indicated lair speed motor unit will apply an air speed signal v'from `the `slider of the variac '552 through rethe balancingsignal.l applied throughfresistor 545 equalsLthe air 'speed signal. v The potential de` 1rlvedsirom:the'slider of variacf552 is` produced by the energization ofi the Windinglofvariac 552 over aicircuit from `,tlf1ef4l'lqpi2 bus-bar, over the contacts ofthe ASrelay" 553 :and `through the Winding of the Variacrtof'ground after the relay 553"foperates *indicative of'an` air` speed. :The air speed effect increases as fthefair speed increases in vandtrat :170 :knots the Wing .flaps motor vunit shaft 526 will assume apo'sition representative of a ZO-'degree deflection. "Duringv .this `speed range the flaps indicatorimotorunit remains in a position representative of the down .position of the wing ii'aps. However, as soon` as the air'speed exceeds 'l'YOflrnots` the "switch assembly 54 of 'the indicated air :speed unitreleasesthereby releasing the FD `re1ay-54'|l-'and causing the FU relay 52| to oper-ate even-though the controls I8 and 4|?, areinxt-heir fdown-positions. Relay 52|, upon' operating-.removes the 'lzialancing potential applied fromtheebalancing potentiometer 521 yand appliesasignalfof vphase (p2 through resistor 524 which is inphase Withftheiai-r` speed signal 'derived from thevariacr'5521arid the motor of the control z circuit ,563 thereupon .operates ythe shaft 526 to the position-representing the upper position oftheswing flaps. Relay '52| also causes the wingapssindicator'motor circuit to operate in the manner-previously described to Acause the indicatorsI 204 landfflifil' to` show the full up posi- ,tion of the'winga-ps. `'Ihissimulates the movement lof the .wing'apssresul-ting from the thigh speed movement-ofthe 'airplane through the air.

What is:,clairned is:

' l. In'an :aircrafttrainer for ight personnel, means for simulating theopera-tion of theY engine fof an airplane, asOurceorcurrent, a: control conductor, means controlled by said frstfmeans for deriving; a po|'.entia`.l-froml said source and for applying f it "'to' ksaid .conductor in simulation of the application of 'hydraulic 'pressure to the hydraulic system of "saidrairplane by an engine driven pump, a motor responsive tosaid potential,l a shaft driven'by said motor to positions representative 'of ksimulated hydraulic pressures, relay means for removing said potential from said conductor toi'arrestkthe'operation of said motor whenV said shaft'has been rotated to a position representative of `a denite pressure in simulation of the operation of the unloader valve of an airplane which limits the build-up of pressure by the enginedriven pump, and cam -operated switches operable byfsaid lshaft to control saidrelay means.

V2. In an aircraftftrainer for flight personnel, means'or simulating the operation of the engine of an airplane, a source tif-current, acontrol conductor, means controlled by said rst means for deriving a potential from said source and for applying it to said conductor in simulation of'the application of hydraulic pressure to the *hydraulic system of said airplane by an -engine driven pump,r amotor -responsive to said potential, a'shaft drivenby said motor to positions 'representative'of simulated hydraulic pressures,

alrst relay operable whensaid shaft `has been rotatedto a position representative of an ade- "euate Ahydraulic pressure, a second relay oper- 'able to remove said potential from said conductor `to 'arrest said motor when said shaft has been rotated `to4 aA .'desired: maximum pressure position `in vsin'iulation 'of` the opening of the unloader 'valvezofeanairplanewhich limits the Ibuild-up :of spressure lfby :the :engine .driven 1pump, `andra 

